Create a master action collection for the shortcut editor

This is still a half-way solution, ideally we'd just create actions from
the .action file and fetch those actions in the code where we need an
action, so there's still duplication. If we make the master action
collection the source for new actions, we will also have to make the
krita.action file translatable.

If you create an action which should have an editable shortcut, you need
to add that to a .action file. Make sure that all the text is exactly the
same, so it gets translated in the shortcut dialog.

On closing the shortcut dialog, changed shortcuts are saved. All
mainwindows's actioncollection will re-read the configuration so they
are synchronized. There's no local krita.rc file anymore, so the windows
won't be able to save the shortcuts to the local krita.rc, all shorcuts
are saved in the kritarc config file.

BUG:313218
BUG:342270
BUG:342184
BUG:337368